Whenever I've had problems like that with Net::FTP, it's usually been because a firewall rule or the server type changed, either on my side or the client's, and all of a sudden only passive (or only active) mode works.

If you were using Passive=>1, switch to 0. If you weren't, switch to Passive=>1.

I hope this helps -- if it doesn't, Debug mode will definitely help you sort it out.